Anchoring assemblies for use in securing a threaded bolt or screw in a preformed opening in concrete or cement walls, piers, foundations or the like have been evolved in a variety of forms over the years. Among the most satisfactory of such prior anchoring assemblies are those employing a bolt or screw with an entry end of a smaller diameter than that of a threaded body portion of the bolt or screw. A coil is provided dimensioned to engage the threads of the bolt or screw, and having an exterior diameter larger than that of the bolt or screw when seated in the threads of the body portion of the bolt or screw. In use, the coil is positioned to engage the threads of the entry end of the threaded member or bolt, and the assembly is inserted into a pre-drilled hole of a diameter between the maximum diameter of the bolt and the maximum diameter of the coil. Thereafter, upon turning the threaded member, the coil will be expanded on the larger diameter body portion of the bolt to grip the concrete or cement of the hole to engage therein.
Anchoring assemblies of this type are disclosed in prior U.S. Pat. Nos. 806,406; 906,691; 1,199,624; 3,967,525; 4,309,135; and 4,536,115. All of these previously patented structures serve generally to employ the coil to provide a relatively smooth thread engaging surface within the frangible concrete material so that the threaded bolt or screw may be turned in thread engaging movement within the hole without damaging the frangible hole surface as would be the case with the coil not present.
However, in using these previously developed anchoring assemblies, it is often found that the turning or "torqueing" of the bolt or screw in the assembly as is necessary to affect expansion of the coil into engagement with the frangible side walls of the hole often produces rotation of the coil in the hole. This causes the hole diameter to be reamed, increasing its size so that it often no longer engages the coil. Further rotation of the bolt or screw produces what is referred to as "strip-out" of the assembly, with the entire assembly coming out of the hole.
Gutshall in U.S. Pat. No. 4,309,135 has attempted to solve the problem by providing tabs at the end of the coil formed of a thickness equal to that of the coil wire and extending axially inclined with respect to the coil to increase the frictional engagement between the coil and the hole inside surface to prevent rotation of the coil as the bolt is being torqued. In use, it has been found that this tab which is dimensioned of a thickness equal to that of the wire forming the coil becomes wedged between the outer diameter of the bolt and the hole inside surface occupying a diameter greater than the diameter of the coil which lies in the threaded portion of the bolt. As a result, in hammering the bolt into the hole, the tabs damage the hole wall surface, and any slippage between the coil and the hole, such as often occurs during torqueing of the bolt into the coil, acts to ream the hole to a diameter beyond the diameter of the coil, permitting undesired "strip-out" of the assembly.